What I have mostly noticed is, that with the 3D movies Disney created themselves, they create the story from scratch. For feature length movies Disney sucks at making the story for scratch. Those animated movies of Disney often are based on fairytales, myths, legends and folklore. This means that the stories have a solid base to begin with. And Disney only has to adapt the stories to make them appealing to children. Adults often do appreciate children's movies, but because these movies are based on wellknown stories, they also appeal to the older public.